Two years ago, Gov. David Ige signed into law a bill that directs the state’s utilities to generate 100 percent of their electricity sales from renewable energy resources by 2045 — an ambitious mandate for the most petroleum- dependent state in the nation.

Hawaii’s electricity generation is dominated by fossil fuels. And due to the continued costs tied to importing most of the energy used throughout the state, ratepayers shoulder the highest prices nationwide — more than twice the U.S. average.

But with the clean energy law in place, amid stops and starts, a transition to a fuller, homegrown renewable portfolio for the electricity sector, which promises to better the islands’ economy, environment and energy security, is now underway. For example, today nearly 1 in 3 single-family dwellings here produces power from the sun, with about 80,000 solar systems operating.

Meeting the 2045 deadline also means lowering overall electrical consumption by stepping up efficiency efforts.

Earlier this year, Ige signed an administrative rule for an updated energy conservation code. (After counties sign off on a version of it, the code will guide new construction and a large slice of residential, commercial and state building renovation.) The previous code was based on 2006 state industry standards.

Much has changed since then to push forward green-minded technology.

For example, most lights used 11 years ago were incandescent bulbs. Today LEDs — touted as an energy-efficiency superhero — are the standard, costing a fraction what they did a decade ago and needing a fraction of the energy that incandescents use.

Among significant changes in the code: a new lighting requirement and a “tighter” building envelope (walls, windows and roofs), which more effectively keep the sun’s heat out, said Howard Wiig, an energy analyst in the state Energy Office.

The old code had no residential lighting requirement. Now: 75 percent of the lights must be high efficiency, “effectively barring incandescents,” said Wiig, adding, “This has the secondary effect of reducing the heat load caused by lighting.”

Ramsey Brown, an energy engineer at Hawai‘i Energy, a program that helps reduce electricity use by providing free or low-cost efficient appliances and other products, points to the code’s residential “Tropical Zone” as a step forward.

“This new requirement is a nod back to more simple construction where it incorporates Hawaii’s tropical breezes as a way to effectively cool a home, along with installing large overhangs to shade windows and sliding doors,” Brown said.

For commercial properties, he said, “commissioning (the process of verifying and documenting the meeting of code requirements) will play a larger role moving forward. Buildings have more complexity, such as intelligent lighting and air conditioning controls, which require fine-tuning and accurate adjustments for efficient and comfortable operation.”

It will cost more to build to the new code, but in the case of homes, that spending can be recouped in energy savings in an estimated 4.3 years. Across-the-board statewide savings, according to the state Energy Office, could total more than $1.4 billion in energy costs over the next 20 years.

The Honolulu Star-Advertiser asked Blue Planet Foundation, a clean-energy focused nonprofit, and the state’s dominant electric utility, Hawaiian Electric Co., to weigh in on progress toward the state’s renewable goal.

WHAT DO YOU SEE AS THE TOP STRIDES SINCE THE 2015 LAW TOOK EFFECT?

Jeff Mikulina, executive director, Blue Planet Foundation:

First, simply setting the 100 percent renewable goal reshaped the energy agenda in Hawaii. It changed the conversation about what’s possible — not only in Hawaii, but elsewhere around the globe (California, for instance, is currently deliberating an identical 100 percent mandate). By setting the 100 percent vision, energy stakeholders were able to move past unproductive squabbles about where we are headed so that we can work productively on the “how” details. The law has fostered collaboration and aligned our energy planning with climate reality.

Second, with the law on the books, Hawaii has telegraphed that it is open for clean energy business and innovation. We saw the results of this when the utility cooperative on Kauai, KIUC, inked deals for some of the first-ever solar plus storage projects. These are game­changers on our journey to 100 percent renewable, upending traditional beliefs about clean energy (not dependable, too expensive).

What makes these projects remarkable is not only that they will provide solar energy at night, but they will provide solar at night at prices that beat fossil fuel. The first project with Tesla, which came online this year, provides 13 megawatts of power and 52 megawatt- hours of energy at a price of 13.9 cents per kilowatt-hour. The second project with AES (the same company that owns the coal-fired power plant on Oahu), currently under development, is twice as large in size and storage capacity — but at a lower price of 11 cents per kilowatt-hour. … Our cleanest energy future may also be our cheapest.

Scott Seu, senior vice president of public affairs, Hawaiian Electric Co.:

The 2015 RPS (renewable portfolio standards) mandate was that 15 percent of electricity sales had to come from renewables, and we exceeded that and hit 23 percent. The three Hawaiian Electric Companies are now at 26 percent and we’re still moving forward. Hawaii Electric Light is at 54 percent, the highest in the state, and Maui Electric is almost at 40 percent.

I’d say another important success is how we’ve revamped how we talk to our customers and other stakeholders on creating the roadmaps for getting to 100 percent renewables, like the Power Supply Improvement Plan or grid modernization.

The traditional approach for us engineers is that we start by focusing on the operational and technical issues, come up with the plans and solutions, and then we say: “Here you go.” In this day and age people expect a lot more than that; they want more of a say. What we’re trying to do now is to first ask our communities and customers: “What do you want?” and then go from there.

WHAT DO YOU SEE AS THE TOP STALL OR DISAPPOINTMENT?

Blue Planet: Shortly after adopting the 100 percent renewable energy law, the state and utility throttled Hawaii’s biggest clean energy success story: rooftop solar. The policy of net energy metering drove the rapid widespread adoption of solar for households and businesses across the state. In 2007, Hawaiian Electric estimated that through net metering, rooftop solar would grow 20-fold by the end of 2015; instead it grew over 350 times as large as it was in 2007.

… That policy catalyzed over $1 billion in private investment in helping reduce the state’s dependence on fossil fuels. But that solar growth came to a screeching halt in October 2015 when Hawaii became the first state to end the net metering policy. The move devastated the local solar industry, which at one time represented one-quarter of all construction jobs in the islands, forcing the layoff of hundreds of employees. While solar may still rebound with new policies and programs, we’ve essentially taken away the most powerful tool expanding renewable energy and democratizing energy choice.

HECO: In the early days of our clean energy movement there was quick progress almost across the board. Anything from adding rooftop solar to wind farms to solar farms to expansion of geothermal and waste to energy. But as we added renewables, we started to experience technical challenges and had to slow things down while we figured those out, because above all, the lights have to stay on. We’re making really good progress and pushing ahead, but I think everyone would like this to move faster.

The other area where I wish we’d make quicker progress is getting clean energy to become a true third leg of our economy alongside tourism and government, where clean technologies and intellectual property are actually created and produced in Hawaii, and we export this know-how so that revenues flow into the state. We can be so much more than just consumers of clean tech developed outside Hawaii. It would be great to marry up our clean energy policies with economic development policies.

WHAT ARE YOUR THOUGHTS ON THE UPDATED ENERGY CONSERVATION CODE?

Blue Planet: While we are supportive of this critical update … Blue Planet Foundation recognizes that the new building standards don’t go far enough — they leave a lot of money (and energy waste) on the table, and they aren’t anticipating the coming evolution of how buildings interact with the energy grid.

Buildings built today will be with us in 2045 and beyond. We should strive for zero net energy buildings — or even energy positive buildings that produce more energy than they consume. New buildings today should enable the building to interact with the modern energy grid, including “demand response” control technologies (that turn off noncritical loads for a short period to help balance the energy grid) and technologies that are responsive to dynamic energy pricing.

Also, buildings should have grid-interactive electric vehicle (EV) charging infrastructure, or at least be “EV ready,” to smooth the deployment of our renewable transportation future.

HECO: This (updated code) is a good thing, in that it reminds us all of the critical importance of energy efficiency. The cheapest kilowatt-hour of electricity is the one that you don’t use, and I really believe that too much of our attention gets focused on how we produce more renewable energy.

The mantra has always been to invest in energy efficiency first — lighting, smart thermostats, solar hot water — since you get more bang for your buck, and then you work on renewable energy generation. Without energy efficiency, our 100 percent renewable energy target will be much higher, and getting there will be much more expensive.